Cover crop termination depends on size

Cover crops provide many benefits, ranging from soil health to erosion control, and can also be an important tool in an integrated weed management program.

However, termination of cover crops is an important factor to consider to ensure that they don’t hurt your cash crops yield, said Andy Luke, University of Missouri Extension regional field specialist in agronomy.

A multi-state study looking into herbicide options to control cover crops was recently published. Systemic herbicides such as glyphosate are able to translocate throughout the plant and kill the growing point of the grass. Glyphosate mixed with Select (clethodim) provided the greatest control across all grass species.

For legume cover crops, tank mixing any of the base control programs (glyphosate, Gramoxone or Liberty) with a synthetic auxin herbicide such as 2,4-D or dicamba resulted in excellent control.

Another question often asked is whether a residual herbicide should be included in a cover crop burn-down application. This will depend on the size of the cover crop at termination.

For smaller cover crops (12-18 inches), it is recommended to include the residual in the burn-down application. While the cover crop will interfere with the residual herbicide reaching the soil surface, rain and a quick breakdown of the cover crop will allow most of the herbicide to eventually reach the soil.

For larger cover crops it is not recommended to include a residual herbicide. The extra biomass can provide early-season weed suppression until a POST herbicide application with a residual is made.

For fields with an uneven cover crop stand, growers may consider using a residual, even with a larger cover crop.